Wear-resisting ceramic composition



Patented June 18,1940 l l l v .UNITED srarss, rarest orrics William B. Donahue, Ossining, N. Y., assignor to Feldspathic Research Corporation, Newm York, N. Y,, a corporation of Delaware i No Drawing. Application September 1, 1937,

Serial No. 161,968

10 Claims. (Cl. 106--11) This invention relates to ceramic compositions, manufacture of grinding balls, which is one of its and has for its object to provide an improved principal uses, although it will be understood composition of this type having extreme toughthat the invention is capable of various other ness and long-wearing qualities which render it uses as referred to above.

- particularly suitable for use in the manufacture In constructing my zircon body I have used a 01' grinding balls as well as for the linings of large number of glass or fired bonding agents ball mills and other purposes where .wear-resistcovering the entire field of glass bonds. In this ing properties are of paramount importance. manner I have determined that any suitable type There has long been a demand in the ceramic of glass forming bonding agent may be satisarts for an economical composition having suffactorily employed, provided the firing tempera- 10 ficient toughness and wear-resisting properties ture is so regulated as to produce zero absorption. for use in grinding balls such as are used in ball For example, the follow n types o a s W e mills for grinding or pulverizing feldspar and investigated'and proved entirely satisfactory for other minerals, as Well as for linings of such mills my purp s which, like the grinding ballsthemselves, must be TABLE I p i capable of withstanding rough usage over long periods of time. l A. A commercial frit, known as Ferro No. 3187,

Aside from the matter of cost, which is an im- Composed of flint a and boric acidportant consideration in products of the type This represents the high B203 type of glassl0 'F there are two m l' f requisites that B. A commercial frit, known as FerroNo. 3134, a grinding ball or ball m11l lmmg must have. Composed f flj t b r x and Whiting This These are (I) absolutely non-porous body to pre- I represents the high c o (lime) type of vent absorption of coloring oxides; (2) must be glass chip and Wear resistant. Ordinary types of 26 natural and artificial materials, particularly the A fut havmg the empmcal forlmflm porcelain grinding balls andlinings of ball mills .3Pb0 in common use today, do not fulfill these require- Q'IMgO} 413203 338102 m r t to the degree eXDeotedohd d s e y This represents the high magnesia (MgO) (lelialfilic manufacturers}.1 th and medium lead (PbO) type of glass.

'0 ave discovered t a zircon, w en bonded by a fired or glass bond, possesses to aremark- A mt having the empmcal formula" able degree the foregoing characteristics as well .6Pb0 If 23203 2 5si02 as many other advantages which render it pe- AMIgO p culiarly suitable for the manufacture of grinding balls, the linings of ball mills, and other purposes Thls replesentsf the hlghlead type ofglass' 35 where similar characteristics of toughness, im- The above represents all types of glasses and perviousness and long wear are-essential. Aparglass Hits. e Compositions of which can be ticular advantage of my zircon bodies bonded Changed as follows: The and P190 with a fired or glass bond is the low firing term can t ly e repl y 110, r the m perature which averages about cone 1, whereas Pbo Can e replaced by the Nazo and K20 40 theporcelain bodies heretofore used for similar in Various e fi 203 C tent n purposes must be fired to cone 10 t 12,, Th all of these glasses is required to make a tough, easiest and least expensive stage of firing is up insoluble glass, resistant to Shook, but y e to come 1, above which the firing involves a conreplaced y 203 0 other f h mph t ric 5 siderable expenditure of time and money, espeoXideS- The amount of Silica p y s he L cially around gone 10, amount used in glasses fired to pyrometric cone Prior to my discovery,.I investigated cold set- Glasses frills of the p e p oye n ting unfired bonds for zircon, including litharge pyrometric o 1445 p c a la s a e also and glycerol, chromic oxide, and phosphoric acid, Covered y the above l 't n D but the results showed that none of these pro- Investigation has Shown that the e f duced a sufficiently strong bond, nor did they solubility of the zircon (during firing) in the produce a zircon body of the desired low porosity. glass employed, is not important so long as the In describing my invention of a zircon body firing temperature of the material is such that an bonded by a fired or glass bond, I will dwell parabsolutely non-porous product is produced. It ti'cularly on the use of my new composition in the was also determined that sodium silicate is not satisfactory, either alone or in conjunction with the above frits, as a medium to given strength in the dry state prior to firing. Sodium silicate causes the structure of the fired body to be vesicular, which is extremely detrimental. It was found that a high grade clay, preferably a plastic kaolin of the Florida type, or a ball clay'low in iron, is best employed to produce workability and strength in the unfired state.

A wide range of the amount of frit necessary to produce zero absorption was investigated. It was found that 15 to 20 parts of frit per 100 parts of zircon was most satisfactory, and that 4. to 7 parts of the plastic clay was desirable to give good workability.

Examples of the most manufacture of grinding invention are as follows:

100 I parts zircon 15-20 parts of any one, or combination of, the

\ glasses such as given in Table I desirable mixes for the balls according to my 4-? parts of high grade plastic clay.

The product is fired to the correct firing temperature which varies with each frit or combination thereof. For instance, the frits in Table I are best fired to 1850-1950 F. for frit A and frit B; 2100-2150 F. for frit C; 2050-2100 F. forfrit D. Smaller amounts of frit can be used with higher firing temperatures; however, in

- such case balls of inferior qualities are produced.

when compared Methods of forming Properties of the zircon grinding ball Zircon grinding balls constructed according to my invention have exceptionally good properties to porcelain balls of the type in common use today. These properties are given in Table II.

TABLE II Property Porcelain ball Zircon ball Color White Grayish white. Absorption Zero Zero. Specific gravity 2.? 2.4 3.8-3.9 (64%heavier). Hardness. ZlICOIl slightly harder than porcelain. Toughness Porcelain balls more easily chipped than ZlICOIl. Rattler loss Porcelain balls lost 40-45% more than the w I zircon balls.

Rate of mill1ng Zircon balls will grind 1500-1700 pounds of material in the same time that porcelain balls will grind 1000 pounds; i. e., 50-60% faster. The zircon balls will lose only 50% as much weight per 1000 pounds of milled material as the porcelain balls.

- Two of the above properties are worthy of special note. These are: (1) toughness; (2) rate of milling. One of the strongest claims for porcelain balls is their freedom from chipping. The

I zircon balls are considerably tougher than porcelain as tested by a sharp blow with a hammer.

This property will insure the user against breakage of balls in the mill and also against the replacement of broken As a result the cost of ball inspection will be reduced, and the efficiency of milling will be increased.

As stated in Table II, tests indicate that zircon balls will mill 1500-1700 pounds of material in the same time required to mill 1000 pounds with porcelain balls. It was also stated that, per 1000 pounds of material milled, the porcelain will lose three to four times as much volume as the zircon. These properties are derived from the wearing quality of the zircon and the bull; specific gravity. This information is further elaborated in Table III.

TABLE III Porcelain ball Zircon ball Pounds of balls to charge mill (equal number of balls) 2000 Cost if both sell at $200 per ton $200. 00 $320. 00 Relative weight of material milled per mill charge of balls 1000.0 2200. 0

Relative cost per pound of milling based on mill charge and cost of balls..... 100 Relative efficiency based on above Porcelain balls cost 1% times item. as much per 1000 pounds ofmaterial milled as the zircon balls.

According to this table, it will cost the user /3 more for the balls per pound of material milled if porcelain is used instead of zircon. This is a substantial saving in the total cost of milling.

Zircon through 100 on 200 mesh, per ton $60.00

balls after each mill run.

been computed,

Zircon through 325 mesh per ton l 00.00 Frit through 100 mesh "per ton 120.00

Clay per ton 8.00 Manufacture, selling, etc per ton of balls 20.06 The cost of manufacturing one ton of balls will be: p

Zircon through 100 on 200. mesh (1 200 lbs.) I $3 Zircon through 325 mesh (400 lbs.) 20.00 Frit (320 lbs.) 19.20 Clay lbs.) .32 Manufacture 20.00.

Total cost 95.52

These figures are based on a mix of the composition:

Per cent Zircon through on 200 mesh 60.0 Zircon through 325 mesh 20.0 Frit .16.-0

, C1ay 4.0

grains determines somewhat the amount of frit zircon available at the lowest this one size of grainballs was very uniform. In

necessary to produce zero absorption. However, no limits or restrictions are necessary on the size of grains employed.

Method of mixing In constructing grinding balls and other materials according to my invention, all the pulverized materials, zircon and frit. are mixed thoroughly in the dry state. The clay (through 20 mesh), and the plasticizer when used, are made into a thin slip. This slip is then added to the zircon and glass and thoroughly mixed. In the dry press mixes, no water other than that in the slip is added. In the stiff mud mixes, water is added to produce the desired consistency.

Method of forming The dry pressed balls. are formed in a special die under pressures varying from 2000 to 10,000 pounds per square inch. p

The stiff mud mixes are first made into balls, approximately round, byhand and then pressed intoa spherical plaster mold. These balls exhibited a poor structure. because of nodules formed in the hand mixing. Because of this defective structure the plastic mix was run through a small pressure pug mill and the balls formed from the pugged mass. The structure of these a commercial operation, the mix should be run through a de-airing pug mill and extruded as a cylindrical bar. The desired weight for each ball would be cut from this bar and formed into the ball by rolling or pressing.

Method of drying and firing The formed balls are taken from the plaster mold and placed in a dryer operated at 150 F. No drying troubles are encountered.

The thoroughly dried balls; are placed in a gas fired muflle kiln and fired according to a predetermined schedule (200 F. per hour) through the temperature range from 1850 to 2250 F. Draw trials are taken at 50 intervals. The correct firing temperature for each mix is determined from data obtained on the balls drawn at each temperature.

It was found from the first series of the foregoing test trials that 15 to 20 parts of fruit were necessary. A second series of balls were prepared, containing 16 per cent frit. and fired in the down draft kiln to a predetermined, correct temperature. The heat washeld for one hour at the maximum temperature and then cooled rapidly to 1300" F. Five hours were required to cool from 1300 F. to 1000 F. This method of cooling served as an annealing period.

In testing zircon grinding balls prepared according to my invention, a rattler of the type employed in testing the resistance to abrasion of crushed stone and gravel was used. Five zircon, and then five porcelain balls, were placed in the chamber with ten 1% inch steel balls. The rattler was then given 8000' revolutions and the loss in weight of the balls determined. As another simple test, a fired ball of each mix was struck five sharp blows with a one pound hammer, and the ease and degreeof chipping was compared to that of a porcelain ball with the results referred to above.

It will be evident that various changes may be made in the compositions and methods of manufacture herein described without departing from the scope and spirit of my invention which is to be limited only by the appended claims when interpreted in View of the prior art.

The invention claimed is:

l. A non-porous wear resisting ceramic composition consisting of unfused zi con bonded by a glass bond.

2. A raw batch for making a non-porous wear resisting ceramic composition consisting of zircon, clay and a glass frit.

3. A raw batch for making a non-porous wear resisting ceramic composition consisting of zircon, kaolin and a glass frit.

4. A raw batch for makinga non-porous wear;

resisting ceramic composition consisting of zircon, a ball clay low iniron, and a glass frit.

5. A non-porous wear resisting ceramic composition consisting of substantially 100 parts of unfused zircon and -20 parts of a glass bond.

6. A grinding ball consisting of unfused zircon bonded by a glass bond.

7. A raw batch for making grinding balls consisting of zircon, clay and a glass frit.

8. A raw batch for makinggrinding balls consisting of zircon, kaolinand a glass frit.

9. A raw batch for making grinding balls consisting of zircon, a ball clay low in iron, and a glass frit.

10. A raw batch for making grinding balls consisting of the following ingredients in substantially the following proportions: 100 parts zircon, 4-7 parts clay, and 15-20 parts of a glass frit.

WILLIAM B. DONAHUE. 

